1. Technical Field
The present invention relates to a capacitive input device capable of detecting a finger touch position as a change in capacitance, a display device with an input function, and an electronic apparatus.
2. Related Art
In electronic apparatuses such as a cellular phone, a car navigation system, a personal computer, a ticket-vending machine, a banking terminal, and the like, a tablet-shaped input device has recently been disposed on a surface of a liquid crystal device to permit information according to an indicative image displayed in an image display region of the liquid crystal device to be input by touching, with a finger, a display position of the inductive image while referring to the indicative image.
Such an input device (touch panel) is a resistance film type, a capacitive type, or the like. However, a resistance film-type input device has the disadvantages of a narrow operating temperature range and weakness to changes with time because in a two-layer structure including a film and a glass, the film is pressed to cause short-circuiting.
In contrast, a capacitive input device has an advantage that a light-transmitting conductive film may be formed on a substrate. Such a capacitive input device is, for example, a type in which electrodes are extended in directions crossing each other so that when the device is touched with a finger or the like, a change in capacitance between the electrodes is detected to detect an input position (for example, Japanese Unexamined Patent Application Publication No. 2007-122326).
Alternatively, the capacitive input device is a type in which alternating currents with the same phase and same voltage are applied to both ends of a light-transmitting conductive film so that when a finger comes in contact with or close to the device, a weak current flowing due to the formation of a capacitor is detected to detect an input position.
In the capacitive input device, for example, a substrate and an electrode which are excellent in light transmittance are used for visualizing an image displayed on a liquid crystal device from the input side of the input device. However, when a large difference in reflectance occurs between a region where a light-transmitting electrode or the like is formed and a region where a light-transmitting electrode or the like is not formed, the presence of the light-transmitting electrode undesirably becomes noticeable. Also, when first and second light-transmitting electrodes are formed on the front and back surfaces of a light-transmitting substrate, a region where the first light-transmitting electrode is formed, a region where the second light-transmitting electrode is formed, and a region where such a light-transmitting electrode is not formed have significant differences in optical configuration because the light-transmitting substrate is interposed between the first and second light-transmitting electrodes, resulting in a problem that a large difference in reflectance occurs between these regions, and the presence of the light-transmitting electrodes becomes noticeable.
Further, even when a first and second light-transmitting electrodes are formed on the same surface of a light-transmitting substrate, a region where the light-transmitting electrodes are formed and a region where the light-transmitting electrodes are not formed have a significant difference in reflectance because of a large difference in refractive index between a glass substrate generally used as the light-transmitting substrate and an ITO film (Indium Tin Oxide) generally used as the light-transmitting electrodes, and thus the presence of the light-transmitting electrodes undesirably becomes noticeable.